A number of processes have heretofore been used or suggested for removing metal from an ore. One method in use is to mine the ore by surface workings employing blasting and steam shovel methods. The ore is then delivered to the plant and crushed. The crushed ore is then charged into large concrete leaching vats in which a leaching solution has been prepared or into which the leaching solution will be charged.
The leaching operation takes place in two stages. In the first stage, the copper is dissolved from the ore, and the second stage consists of washing or displacing from the leached ore the water soluble copper that remains. Strong solution resulting from the leaching of the ore is high in copper, low in acid, and is then transported for electrodeposition of part of the copper content.
A similar process is used for the electrowinning of zinc.
Cadmium is found in very small quantities in most ores. It can be profitably produced only as a by-product in the manufacture of some other metal. Cadmium can be recovered from a cadmium-copper-zinc precipitate. The precipitate can be leached with sulfuric acid solutions to dissolve out cadmium and zinc, and the cadmium can be precipitated out of solution by sheet zinc. The precipitated cadmium is then washed and dissolved in an acid electrolyte in which form it is passed to a purification and iron removal system and from there the cadmium is electrodeposited.
After the copper or other metal electrolyte solution is formed, it is necessary to extract the copper or other metal from the solution. One method to accomplish the separation of the metal from the electrolyte solution was suggested by Anderson et al as disclosed in the U.S. Pat. No. 3,483,568. In this patent, there is discosed a plurality of anodes which are suspended in the electrolyte; spaced therefrom are a plurality of cathodes which are comprised of flat sheets parallel to each other. Electrolyte is forced through ports below the cathodes and anodes such that the fluid electrolyte moves successively towards and across the face of an anode and thereafter across the face of a cathode. An electric potential is maintained between the anode and cathode and as the metal is drawn out of the solution, it accumulates on the cathode. One of the problems facing the industry is that accumulations build up on the cathode which are called dendrites, small areas which protrude from the plated cathode and extend toward the anode. When the dendrite becomes long enough it causes a short and the system fails. Further, such a copper deposit is commercially unacceptable, with any type of large dendritic structures.
The present invention provides a unique approach to materially lessening the possibility of dendrite growth by utilizing a vortex diffuser. The vortex diffuser supplies a fluid such as air or electrolyte and creates positive and negative pressures to produce unique effects on a cathode plate which ionically removes the metal from the electrolyte. By using a vortex diffuser, a separate anode can be eliminated from the electrolytic bath, because the vortex diffuser itself functions as the anode and relatively high current densities can be used.